Messages in this thread | | | Subject | Re: [PATCH] arm64: dts: rockchip: decrease rising edge time of UART2 | From | Katsuhiro Suzuki <> | Date | Mon, 4 Mar 2019 22:56:46 +0900 |
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No problem! Thank you for discussion :)
On 2019/03/04 4:12, Tony McKahan wrote: > On Sun, Mar 3, 2019 at 1:45 PM Tony McKahan <tonymckahan@gmail.com> wrote: >> >> Hello Katsushiro, > > And apologies for the extra "s", typing too quickly I'm afraid. >> >> On Sun, Mar 3, 2019 at 12:31 PM Katsuhiro Suzuki >> <katsuhiro@katsuster.net> wrote: >>> >>> Hello Tony, >>> >>> On 2019/03/04 0:13, Tony McKahan wrote: >>>> On Sun, Mar 3, 2019 at 9:04 AM Katsuhiro Suzuki <katsuhiro@katsuster.net> wrote: >>>>> >>>>> Hello Heiko, >>>>> >>>>> Thank you for comments. >>>>> >>>>> On 2019/03/03 22:19, Heiko Stuebner wrote: >>>>>> Hi, >>>>>> >>>>>> Am Sonntag, 3. März 2019, 13:27:05 CET schrieb Katsuhiro Suzuki: >>>>>>> This patch increases drive strength of UART2 from 3mA to 12mA for >>>>>>> getting more faster rising edge. >>>>>>> >>>>>>> RockPro64 is using a very high speed rate (1.5Mbps) for UART2. In >>>>>>> this setting, a bit width of UART is about 667ns. >>>>>>> >>>>>>> In my environment (RockPro64 UART2 with FTDI FT232RL UART-USB >>>>>>> converter), falling time of RockPro64 UART2 is 40ns, but riging time >>>>>>> is over 650ns. So UART receiver will get wrong data, because receiver >>>>>>> read intermediate data of rising edge. >>>>>>> >>>>>>> Rising time becomes 300ns from 650ns if apply this patch. This is not >>>>>>> perfect solution but better than now. >>>>>>> >>>>>>> Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net> >>>>>>> --- >>>>>>> arch/arm64/boot/dts/rockchip/rk3399.dtsi | 9 +++++++-- >>>>>>> 1 file changed, 7 insertions(+), 2 deletions(-) >>>>>> >>>>>> your changing a core rk3399 property here, so I'd really like to get >>>>>> input from other board stakeholders on this before applying a core >>>>>> change. >>>>>> >>>>>> Could you either include the submitters of other rk3399-boards in the >>>>>> recipient list so that they're aware or limit the change to rockpro64 for >>>>>> the time being (aka overriding the property in the board-dts) please? >>>>>> >>>>> >>>>> OK, I'm adding other boards members. >>>>> by ./scripts/get_maintainer.pl arch/arm64/boot/dts/rockchip/rk3399-*.dts >>>>> >>>>> >>>>> RockPro64 directly connect UART2 pins of RK3399 to external connector. >>>>> I think maybe other RK3399 boards are facing same problem, but I cannot >>>>> check it because I have RockPro64 only... >>>>> >>>>> I'm happy if someone tell me other boards situation. >>>> >>>> I'm pulling out other rockchip boards momentarily to see what kind of >>>> population we have. >>>> >>>> Note these are not all running 5.x kernels, however none of them have >>>> the UART2 drive levels modified to my knowledge, and regardless, none >>>> show over 100 ns. >>>> >>>> board: rise/fall >>>> >>>> rk3399-roc-pc: 90ns/90ns >>>> rk3399-rockpro64 V2.0: 90ns/45ns >>>> rk3399-rockpro64 V2.1: 40ns/41ns >>>> >>>> Please make sure there's not a large amount of flux or something >>>> around the terminals on your board, that seems excessively high. >>>> >>> >>> Thank you for valuable information. For more deeply discussion, >>> I tried other conditions and watch the rise/fall times. >>> >>> 1) Not connect >>> The rise/fall times are 40ns/5ns when nothing connect (impedance is >>> very high) to external pin of RockPro64. >>> >>> What UART device are you using with RockPro64? If you use some device >>> with RockPro64 and board shows rise/fall times = 90ns/45ns, my device >>> is not suitable for RockPro64 by some reason. So it's better to drop >>> my patch. >> >> The adapter is an FTDI FT232RL breakout board, attached with some >> generic Dupont connector jumpers. >> Interesting your RockPro is showing this symptom, perhaps there is a >> cold solder joint somewhere introducing resistance? >> >>> >>> 2) Other SoC >>> I have other SoC board rk3328-rock64, Rock64 shows rise/fall times = >>> 90ns/80ns when same UART-USB device is connected to UART pin. >> >> I measured similar on my Rock64 as well. >> >>> >>> I think it shows rk3399's (or RockPro64's?) drive strength is a little >>> weak. So it's better to increase the drive strength of UART of rk3399. >> >> I do not think this is a bad idea generally, it simply allows for more >> available current from the interface. I'll let others be the judge of >> that, however. >> >>> >>> Best Regards, >>> Katsuhiro Suzuki >>> >>>>> >>>>> Best Regards, >>>>> Katsuhiro Suzuki >>>>> >>>>> >>>>>> Thanks >>>>>> Heiko >>>>>> >>>>>> >>>>>> >>>>>>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi >>>>>>> index beaa92744a64..e3c8f91ead50 100644 >>>>>>> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi >>>>>>> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi >>>>>>> @@ -2000,6 +2000,11 @@ >>>>>>> drive-strength = <8>; >>>>>>> }; >>>>>>> >>>>>>> + pcfg_pull_up_12ma: pcfg-pull-up-12ma { >>>>>>> + bias-pull-up; >>>>>>> + drive-strength = <12>; >>>>>>> + }; >>>>>>> + >>>>>>> pcfg_pull_up_18ma: pcfg-pull-up-18ma { >>>>>>> bias-pull-up; >>>>>>> drive-strength = <18>; >>>>>>> @@ -2521,8 +2526,8 @@ >>>>>>> uart2c { >>>>>>> uart2c_xfer: uart2c-xfer { >>>>>>> rockchip,pins = >>>>>>> - <4 RK_PC3 RK_FUNC_1 &pcfg_pull_up>, >>>>>>> - <4 RK_PC4 RK_FUNC_1 &pcfg_pull_none>; >>>>>>> + <4 RK_PC3 RK_FUNC_1 &pcfg_pull_up_12ma>, >>>>>>> + <4 RK_PC4 RK_FUNC_1 &pcfg_pull_none_12ma>; >>>>>>> }; >>>>>>> }; >>>>>>> >>>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Linux-rockchip mailing list >>>>> Linux-rockchip@lists.infradead.org >>>>> http://lists.infradead.org/mailman/listinfo/linux-rockchip >>>> >>>> >>> > > _______________________________________________ > Linux-rockchip mailing list > Linux-rockchip@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-rockchip > >
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